The USA's number one crop - corn - could see its prime growing region shift to the Canadian border or its price volatility increase sharply within 30 years, with Noah Diffenbaugh, Tom Hertel and their colleagues pointing to climate change as the cause. Credit: Doug Wilson, Agricultural Research Service, USDA

Climate change is set to cause big swings in the price of corn grown in the US from year to year, researchers have said this week. That’s largely because temperatures above 29°C during certain points in the corn growing season reduce the amount produced, said economist Tom Hertel from Purdue University in West Lafayette, Indiana. But it will also be affected by how corn growers react and what the government does, he and his co-workers have found. “Corn prices have been fairly volatile in the last couple of decades,” Tom told Simple Climate. “That is nothing compared to what we would see under future climate, assuming that nothing else changed.”

In 2009, scientists showed that crops like corn were very sensitive to extreme heat, and that in a warmer world today’s plants would suffer. However, those studies didn’t show how smoothly or otherwise heat would change prices and output, or yield, of crops. Governments and farmers might like to know this to help their planning, but predicting warming’s impact on corn requires a very detailed picture of what future temperature might be like. “It’s not whether the temperature on average in a month or year was high, it’s whether you have a few hot days and whether those come at a time when they do significant damage,” Tom said. “If you talk to farmers they’ll certainly tell you, those really hot days coming at critical times can be very damaging.” Read the rest of this entry »

Also known as laughing gas, nitrous oxide (N2O) is a powerful greenhouse gas, and bringing its release under control will need the world to make very serious changes. That’s what Eric Davidson, executive director at the Woods Hole Research Center in Falmouth, Massachusetts, has found by looking at likely future N2O emissions.

Improvements in farming, industry and transportation could help reduce levels of the gas from what they might become. So too could the hard-to-swallow suggestion for many that people in the world’s richest countries halve the amount of meat they eat. But to meet the hardest target scenario to be used in an important climate report scientists are working on, we need to do all of these, Eric says. “Mitigating N2O emissions will be a huge challenge, and I’ve outlined the scope of the magnitude of change necessary,” he told Simple Climate. “They are not outside the realm of possibility, although they will be very challenging.”

In 2008, the UN Intergovernmental Panel on Climate Change (IPCC) agreed it would produce its fifth assessment report looking at global warming in detail by October 2014. To try and predict what will happen in the future, the scientists involved have drawn up four “representative concentration pathway” (RCP) scenarios that humanity could follow. These are based on a range of values for how much the atmosphere would be heating up in 2100. But there has been little work so far to see what will need to happen to reach the greenhouse gas levels these scenarios imply. Read the rest of this entry »

Comparing predictions and measurements of the effects of climate change on plants and animals over the past five years shows predictions calling it “one of the major threats to global biodiversity” are accurate, and possibly optimistic, according to the University of Exeter's Ilya Maclean. The risk from climate change to moths, and other members of the order "lepidoptera", like butterflies have been relatively well studied, but for other insects knowledge remains scarce. Credit: Ohio State University

Humans’ success at spreading across the world has long worked with changes in climate to doom other animals. Our hunting is one cause suggested by scientists of big mammals like woolly mammoths disappearing about 10,000 years ago. Other researchers say that climate drove some creatures extinct, while human hunger made things worse for others. But now that humans are changing the climate and competing with animals for space, food and other resources, we pose them a double danger.

Since Simple Climate started, I’ve regularly reported how man-made climate change is further eroding the variety of life on Earth. That variety is considered to indicate the planet’s health. This week, I thought I’d bring together a few pictures as a reminder of which creatures are at risk. Hopefully, they’ll provide a little extra motivation to cut greenhouse gas emissions and reduce the pressure these animals are under. Click on the pictures to read the original blog posts. Read the rest of this entry »

Previous data suggesting that the world started warming out of the last ice age before CO2 levels in the atmosphere started rising don’t show the full picture. That’s according to US, French and Chinese scientists who have added to those Antarctic measurements with more taken from 80 locations across the globe. Harvard University’s Jeremy Shakun and colleagues show the greenhouse gas rises before temperature, supporting the case that CO2 drove climate change then, as it is now. “This provides a very tangible example of what rising CO2 can mean for the climate over the long term,” Jeremy said.

In the 1980s, researchers began building the history of CO2 in the atmosphere from cylinders of ice drilled from the Antarctic. Bubbles in the ice contain air from the time they formed, which researchers can measure. They can also figure out how old the ice holding the bubbles is from how deep it is in the core. And finally they can also work out temperature from the amount of the different forms, known as isotopes, of elements like hydrogen, carbon and oxygen in the ice. That’s because the temperature at which the snow that eventually became the ice formed affects how much of each it contains. And because some isotopes are radioactive and decay to a more stable isotope with time, studying them gives scientists another way to check the ice’s age.

The 800,000 year record of atmospheric CO2 from Antarctic ice cores, and a reconstruction of temperature based on hydrogen isotopes in the ice. The current CO2 concentration of 392 parts per million (ppm) is shown by the blue star. Credit: Jeremy Shakun/Harvard University

Such methods show temperature and CO2 levels rising and falling together for 800,000 years, Jeremy told journalists over the phone on Tuesday. “The question is: Which is the cause and which is the effect?” he asked. “If you look up close you see temperature changed before CO2 did. This is something the global warming skeptics have jumped on to say, ‘Obviously CO2 doesn’t cause warming because it came after the warming in these records’. But these ice cores only tell you about temperatures in Antarctica. For the same reason that you don’t look at just one thermometer from London or New York to prove or disprove global warming, you don’t want to look at just one spot in the map to reconstruct the past either.” Read the rest of this entry »